With conventional fixing rotary members used in an image formation apparatus, a release layer composed of a fluororesin tube or a fluorine-based dispersion is provided on the surface of an elastic layer composed of a fluororubber, a silicone rubber, or a sponge layer. Of the various rolls used in these fixing rotary members, those used in color copiers and printers must have low hardness in order to improve fixability and better bring out the toner color, which is in keeping with the higher image quality achieved in recent years, and at the same time the elastic layer must be thinner in order to reduce power consumption. Rolls whose elastic layer is softer, thinner, and more flexible have often been used in an effort to meet both of these requirements.
Unfortunately, as the hardness of the elastic layer is lowered, there is more deformation of the elastic layer by the nip between the fixing roll and the pressing roll, until the fluororesin used as a release layer on the roll surface is no longer able to conform to the roll deformation, at which point wrinkles and cracks may develop in the shape of rings or in the axial direction.
Furthermore, the more the hardness of the elastic layer is decreased, the greater is the expansion of the elastic layer due to heat during roll molding, which is a problem in that wrinkles in the axial direction can develop immediately after molding or extremely soon after the start of use in an actual device. Also, a thinner elastic layer is a problem in the case of a tube that shrinks both axially and radially because not enough nip width can be ensured, and offset occurs.